[The subcutaneous vascular system (lower extremity): studies on micro-preparations].

At the level of fascial penetration the cutaneous arteries of the lower extremity are constantly accompanied by 1 or 2 communicating veins of varying diameter. Usually, they penetrate the fascia in rows via the muscular interstitium. There they give up branches to the fascial vascular network, to pre- and subfascial areolar tissue and possibly to the muscle origins on the fascia, or to the intermuscular septa. The texture of the fascia itself determines the structure of fascial openings for the cutaneous vessels. In the subcutaneous tissue the arteries are accompanied by 1 or 2 veins (Vv. comitantes). Numerous arterio-arterial and intervenous anastomoses form a subcutaneous network of vascular bundles. Two anastomosing venous systems can be distinguished in the subcutis: The small Vv. comitantes are fed primarily by the subcutaneous adipose lobes, and end in communicating veins or flow into the subcutaneous veins (epifascial veins). These large subcutaneous veins on the other hand are responsible for the actual outflow from the venous network of the cutis. They form the saphenous system or empty into larger communicating veins. Between the subcutaneous arterioles and accompanying venules there are numerous capillary webs. In addition direct capillaries and looped as well as meandering or knotted arterio-venous shunts are found. The subcutaneous vascular bundles are fixed by a connective tissue. There are often typical capillary meshes within arterial sheat, oriented like a rope-ladder. They undergo prenatal development. The subcutaneous (epifascial) veins are surrounded by areolar tissue on the cutaneous as well as on the fascial side. Fibers from the accompanying connective tissue criss-cross into the adventitia and thereby anchor the veins in a movable fashion. Typical vascular patches with plane capillary networks characterize the areolar tissue around the subcutaneous veins, which is differentiating at the 2nd half of the fetal period. Within are also capillary loops and convoluted arterio-venous shunts.